The invention relates to electronic circuit boards and particularly passive means for protecting against voltage transient in electronic components. Alarm systems and many other electronic devices are attached through wires to external devices. These wires are subject to voltage transients that can lead to failure of individual components on the circuit board. The problem is particularly acute with respect to resistors at an input for a given electronic circuit. Wires that are connected to the input for the circuit, referred to as “external wires” have voltage transients in them. The usual failure mode of such resistors is a changing value of the resistor as the transient arcs from the body of the resistor, burning off the film deposited on the resistor.
Although the present invention will be described in terms of resistors on the input of a circuit board, those skilled in the art will recognize that the present invention may be utilized with other resistors as well as other surface mounted passive components such as inductors and capacitors. This is particularly true of such surface mounted components having end caps.
The invention has particular application to intrusion as well as fire/smoke detection alarm systems. Examples of intrusion detection systems include those shown in the following United States patents having the same assignee as the present application:    U.S. Pat. No. 6,593,850 Wireless intrusion detector with test mode issued on Jul. 15, 2003 to Addy.    U.S. Pat. No. 6,188,318 Dual-technology intrusion detector with pet immunity issued on Feb. 13, 2001 to Katz, et al.    U.S. Pat. No. 4,939,359 Intrusion Detection System with Zone Location issued on Jul. 3, 1990 to Freeman.    U.S. Pat. No. 4,614,938 Dual channel pyroelectric intrusion detector issued on Sep. 30, 1986 to Weitman.    U.S. Pat. No. 4,360,905 Intrusion Alarm System for Use with Two-Wire-Cable issued on Nov. 23, 1982 to Hackett.    RE No. 30,288 Intrusion Detection System issued on May 27, 1980 to Hackett.    U.S. Pat. No. 4,035,798 Ultrasonic Intrusion Detection System issued on Jul. 12, 1977 to Hackett.
Examples of such a fire/smoke detection system 14 include the apparatus shown in the following United States patents having the same assignee as the present application:    U.S. Pat. No. 6,150,935 Fire Alarm System With Discrimination Between Smoke And Non-Smoke Phenomena issued on Nov. 21, 2000 to Anderson;    U.S. Pat. No. 6,084,522 Temperature Sensing Wireless Smoke Detector issued on Jul. 4, 2000 to Addy    U.S. Pat. No. 5,781,291 Smoke Detectors Utilizing A Hydrophilic Substance issued on Jul. 14, 1998 to So, et al.    U.S. Pat. No. 5,764,142 Fire Alarm System With Smoke Particle Discrimination issued on Jun. 9, 1998 to Anderson, et al.    U.S. Pat. No. 5,726,633 Apparatus and Method for Discrimination of Fire Types issued on Mar. 10, 1998 to Wiemeyer;    U.S. Pat. No. 5,659,292 Apparatus Including a Fire Sensor and a Non-Fire Sensor issued on Aug. 19, 1997 to Tice.    U.S. Pat. No. 5,633,501 Combination Photoelectric and Ionization Smoke Detector issued on May 27, 1997 to Amieshi, et al.    U.S. Pat. No. 5,557,262 Fire alarm System with Different Types of Sensors and Dynamic System Parameters issued on Sep. 17, 1996 to Tice.    U.S. Pat. No. 5,117,219 Smoke and Fire Detection System Communication issued on May 26, 1992 to Tice, et al.    U.S. Pat. No. 4,916,432 Smoke and Fire Detection System Communication issued on May 26, 1992 to Tice, et al.    U.S. Pat. No. 4,374,329 Smoke Detector with Test Apparatus issued on Feb. 15, 1983 to Schoenfelder, et al.    U.S. Pat. No. 4,316,184 Combination Combustion-Product Detector issued on Feb. 16, 1982 to Nagel.    U.S. Pat. No. 4,225,860 Sensitivity Controlled Dual Input Fire Detector issued on Sep. 30, 1980 to Conforti.    U.S. Pat. No. 4,097,851 Sensitivity Compensated Fire Detector issued on Jun. 27, 1978 to Klein.    U.S. Pat. No. 4,091,363 Self-contained Fire Detector with Interconnection Circuitry issued on May 23, 1978 to Siegel, et al.    U.S. Pat. No. 4,020,479 Fire Detector issued on Apr. 26, 1977 to Conforti, et al.
The disclosures of the above referred to patents are incorporated by reference. Various embodiments of the present invention may utilize different fire and smoke detecting apparatus as well as different intrusion detection and storage apparatus.
A preferred technique for assembling circuit boards involves the use of surface mount components and wave soldering. The invention has particular application to surface mount components such as resistors. One example of a surface mount component is described in U.S. Pat. No. 5,604,477 entitled Surface Mount Resistor and Method for Making Same issued on Feb. 18, 1997. One specific technique for wave soldering is described in U.S. Pat. No. 4,208,002 entitled Wave Soldering System issued on Jun. 17, 1980. The disclosures of these patents are incorporated by reference.
Typically, the components that will tolerate the voltage transients are relatively high cost large axial mount components. Thus, the traditional approach to avoiding the problem increases the cost for the component and increases the cost of assembly by complicating the assembly procedure. Alternatively, relatively expensive transient absorbers such as transorbs or metal oxide varistors (MOV) may be used. Thus, the traditional approaches to solving the problem increase the cost of the product.